Movable shield structure for vacuum gap devices



J. D. COBINE Jan. 26, I965 MOVABLE SHIELD STRUCTURE FOR VACUUM GAPDEVICES 3 Sheets-Sheet 1 Filed Feb. 23, 1962 Inventor-2 dames D. Cob/he,.b

if A ttorney J. D. COBINE Jan. 26, 1965 MOVABLE SHIELD STRUCTURE FORVACUUM GAP DEVICES 3 Sheets-Sheet 2 Filed Feb. 23, 1962 In van tor:demes D. C'o

ine,

by (F /'s A ttorney.

J. D. COBINE 3,167,629

MOVABLE SHIELD STRUCTURE FOR VACUUM GAP DEVICES Jan. 26, 1965 3Sheets-Sheet 3 Filed Feb. 25, 1962 Fig. /5.

Fig. /4

A I f /n venfor James 0. Cob/he United States Patent Ofiice 3,157,629Patented Jan. 26, 1965 3,1516% MQVABLE SH ELD 'TRUCTURE F; VAQUUM GAPDEVHIES James D. Cobine, liexford, N.Y., assignor to General ElectricCompany, a corporation of New Yorlr Filed Feb. 23, 1962, Ser. No.175,485 '11 Claims. (@Cl. 22-l449 This invention relates to an improvedvacuum device construction wherein a shield element is provided toprotect the vacuum envelope from condensation and nevertheless theelectrodes can be visually examined at will.

This application is a continuation-in-part of my prior applicationSerial No. 79,351, filed December 29, 1960, now abandoned.

In vacuum devices such as switches, circuit breakers and vacuum gaps, avacuum envelope is provided and defines a vacuum cavity. A pair ofelectrodes is located within the envelope and have portions extendingoutside the same for connection to the circuit to be switched orprotected. The electrodes are movable in relation to each other betweena contact-making or circuit-making position and a contact-breaking orcircuit-interrupting position in the case of switches and are spaced todefine a gap in fixed gap devices. When the electrodes are moved inrelation to each other from circuit-making to circuitbrealring positionor when a fixed gap is overloaded, an arc is usually drawn. The aregives rise to somevaporization of the electrode materials and subsequentcondensation thereof. The condensation takes place on the electrodes, onthe inside face of the vacuum cavity, and on other parts exposed to thevapor. In devices designed to carry current until natural current zero(and thus avoid the overvoltages associated with abrupt currentinterruption), the electrodes are designed to provide copious quan-'ties of vaporized material, thus giving rise to a considerable amountof condensation.

When condensation of the electrode material takes place on the insideface of the vacuum envelope, it tends to form a conducting current pathacross otherwise insulating portions of the envelope. These insulatingportions of the envelope must retain their insulating integrity.Otherwise conduction across the switch may take place even through theelectrodes are in a spaced, non-contacting relationship.

in one method of preserving the insulating integrity of the inside faceof the vacuum envelope, a shield is located between the electrodes andthe vacuum envelope. Conventionally, the shield is in the form of acylinder about the electrodes. Frequently, inwardly flaring end portionsare provided to confine the vapor further. The shield is of material andconformation to define a favorable surface for the condensation of theelectrode material vapor. Typically, the shield is of stainless steel.

The ability of a vacuum switch to withstand rapid circuit voltagerecovery depends in considerable measure on the condition of theelectrodes. When the electrodes are smooth and devoid of pitting anderosion, the circuit in terrupting capacity is at a maximum. As thecondition of the electrodes deteriorates with continued use of thedevice, the irregularities on the surfaces of the electrodes form pointsof abnormally high voltage gradient, with the result that the operatingcapacity of the device is reduced. It is accordingly important toinspect such switches and gap devices periodically to assure thatelectrode deterioration has not reached a point wherein the operatingcapacity thereof is unduly prejudiced. This is especially true in thecase of switch or gap device having electrodes with tin, copper, andsimilar low vapor pressure ingredients and hence relative greatsusceptibility to electrode erosion.

In accordance with the present invention, the vacuum device envelope hasat least some portion or" transparent material, such as glass. Theelectrodes are so located within the envelope as to be viewed readilythrough this transparent portion, thus permitting the user to ascertainthe condition of the electrodes through visual inspection. At least onemovable shield element is interposed between the electrodes and thetransparent portion of the vacuum envelope. This is movable between twopositions. One position is the active position in registration with thetransparent part of the envelope. In this position the shield element iseffective to protect the transparent portion of the envelope fromcondensation of the vaporized electrode material. The other position isthe viewing position, where the shield element is out of registrationwith the transparent part of the envelope and thus permit uninterruptedview of the electrode from outside the envelope.

The present invention also contemplates various specific constructionsthrough which the above movable electrode action is achieved.

It is therefore a general object of the present invention to provideimproved vacuum devices using shield elements and in which the conditionof the electrodes may be visually examined at will.

Another object of the present invention is to provide improved vacuumdevices of the foregoing type wherein movable shield elements cooperatewith transparent envelope portions to permit visual electrodeexamination at will.

Still another object of the present invention is to provide an improvedvacuum switch using movable shield elements in cooperation withtransparent envelope portions and in which apparatus extending outsidethe envelope is eilective in cooperation with apparatus in the envelopeto move the shield elements from active to inspecting position.

Another object of the present invention is to provide an improved vacuumdevice using movable shield elements telescopically disposed within thevacuum envelope and movable over the inside face thereof between activeand inspecting positions.

Yet another object of the present invention is to provide an improvedvacuum switch using movable shield elements and including cooperatingelectrode and shield parts effective to move the shield from active toinspecting 1 position upon predetermined electrode movement.

Another specific object of the present invention is to provide animproved vacuum device having two-part shield means in which one partdefines a port in registration with a transparent portion of theenvelope to permit viewing of the electrodes and the other part is acover movable between an active position covering the port and aninspecting position out of registration with the port. Further objectsof the present invention include the provision of improved vacuumdevices having shield elements movable between active and viewingpositions, eii'ective in active position to prevent undesirablecondensation on insulating parts and effective in viewing position topermit viewing of the electrodes, and embodying features ofconstruction, combination and arrangement rendering them suitable forpractical use under a wide variety of conditions, readily manufactured,reliable, and

in other respects forming commercially useful and desirable devices.

The novel features which I believe to be characteristic FIG. 2 is across-sectional view through axis 2:2, FIG. 1, showing the arrangementof the ferromagneuc bars or armatures about the shield.

FIG. 3 is a greatly enlarged fragmentary portion of FIG. 1, showing theroller construction in further detail. FIG. 4 is a view like PEG. 3, butshows a ball and socket construction alternative to the rollerconstruction of FIG. 3, illustrative of the various means that may beemployed to position the shield and permit free vertical movementthereof.

FIG. 5 is a fragmentary view like FIG. 1, but showing an alternativeform of the present invention; with the shield shown by dashed lineswhen in viewing'position.

FIG. 6 is a fragmentary cross-sectional view through axis 6-6, FIG. 5.

FIG. 7 is a fragmentary side elevational view, with parts indiagrammatic form, showing another alternative construction of thepresent invention in which the shield has a stationary part defining awindow and a movable part which in active position registers with thewindow and in viewing position is out of registration therewith.

FIG. 8 is a somewhat diagrammatic cross-sectional view of an alternativeembodiment of the structure of FIG. 7.

FIG. 9 is a greatly enlarged fragmentary portion of FIG. 8, showing thebearing means in the knob to provide for rotation ofthe arm whichterminates therein.

FIG. 10 is a view in fragmentary form, like FIG. 1, but showing stillanother embodiment of the present invention.

' FIG. 11 is a cross-sectional view through axis 11-11, FIG. 10.

FIG. 12 is a view like FIG. 10 but showing the parts in circuit-breaking position.

FIG. 13 is an enlarged fragmentary view taken'along axis 1313, FIG. 10.

FIGS. 14 and 15 are vertical cross-sectional views of a I vacuum gapdevice of the fixed type constructed in accord with another feature ofthe invention.

Referring now to FIG. 1, there is shown at 1 a vacuum envelope defininga cylindrical vacuum space 2. This envelope, asshown, is of insulatingmaterial such as glass 1 and receives at'its inturned upper end thesleeve 3, which .is preferably of fernico and is embedded in the beaded'intu'rned edge of the envelope as shown.

envelope 1 may be of metal with suitable bushings to insulate'electroderods therein from. one another. At its lower outturned beaded edge, theenvelope receives the end cap 4, which is likewise embedded and ispreferably of fernico. The sleeve 3 receives one end 'of the bellows 5in a vacuum-tight seal. The other end of bellows 5 is in vacuum-tightseal with the movable electrode rod 6. The end cap is in vacuum-tightseal with the fixed. electrode rod 7, thereby completing the vacuumenvelope around the space 2. l

Electrode rods dead 7 are each of generally cylindrical constructionextending coaxially ofthe envelope from'outside the envelope to theirrespective headed electrodes 8 and9, which are in cooperating positionswithin the envelope. The electrode rods receive circuit connection 10.and 11, respectively, to the external circuit to becontrolled (notshown).

The electrode rods' 6 and 7 are shown in the spaced circuit-breakingposition in FIG. 1.. That is, the electrodes 8 and 9 are out of contactwith each other and Alternatively margins of the armature elements 19a.

6 in position and to move the same as desired between circuit-making andcircuit-breaking position.

When the electrodes are moved from circuit-making to circuit-breakingposition, an arc is usually struck therebetween and continuesmomentarily. This results in the production of quantities of vaporizedelectrode .material. In the apparatus of FIG. 1, this material tends tocondense on the interior surface of the shield 12, rather than on theadjacent interior faces of the envelope 1. To this end, the shield 12 isof cylindrical construction as shown in FIGS. 1 and 2 to define acylindrical segment of the envelope 1 that is aligned with theelectrodes and is protected from condensation. The shield 12. flaresinwardly at 13 and 14 to define restricted end portions that furtherlimit the extent that vaporized electrode material is free to condenseon the interior of the vacuum envelope. It is rolled at the end tominimize arcing.

The shield 12 is movably positioned within the vacuum envelope 1. It hasa plurality of outwardly extending arms 15, each carrying a wheel 16shown in greater detail in FIG. 3 (or an equivalent means facilitatinglateral motion). As shown in FIGS. 1 and 2, these arms may be in twoaxially spaced groups of four each, thus locating the shield in aligned,centered position in the cylindrical envelope. Alternatively, these arms17, as shown in FIG. 4, may extend outwardly from the shield andterminate in socket portions 18, each of which receives a ball 19 toroll on the cylindrical envelope and similarly locate the shield inaligned, centered positions on the cylindrical envelope.

A plurality of ferromagnetic bars or armatures 1% are located about theperiphery of the shield 12 as shown in F168. 1 and 2. Preferably theseare oriented to define elements of a cylinder and are of sufiicientnumber to form in effect a sleeve about the shield 12. The respectivearmatures are anchored on the shield by the ears 2th as shown in FIG. 2.

Outboard the vacuum envelope there is provided the shield operatingmechanism shown generally at 21. This iechanism is composed of bearing22, arm 23 longitudinally slidable in the bearing, handle, or knob 24 onthe lower end of the arm 23, and permanent magnet 25 carried by the headmember 26 on arm 23. As shown, the magnet 25 defines a pair of oppositepermanent magnet poles spaced to register with the upper and lowerPreferably, the magnet 25 extends in close proximity to the outer faceof the envelope 1 and the armature19a extend to closely spacedrelationship with the inner face of the envelope l'so as to cause amaximum quantity of the flux of magnet 25 to extend through thearmatures.

The shield is movable between an active and a viewing position. Theactive position is shownin the solid lines of FIG. 1. In this positionthe shield 12 is axially aligned with the electrodes 8 and 9 and is thusinterposed between the transparent side of the envelope 1 and theelectrodes. tive to protect the portion 27 of the envelope fromcondensation of vaporized electrode material. The shield 12 is normallyin this active position and thus is effective when circuit-breakingoperations take place.

The other position of shield 12 is the viewing position.

i This is the position shown in the dotted lines of FIG. 1.

When in this position, the upper edge of the shield is below the'upperface of electrode 9 and the electrodes may both be readily visuallyinspected by the user.

The shield 12 is moved between the active and inspecting positions byappropriate motion movement of the knob 24 of arm 23. When this arm isin the up'position (as shown bythe solid lines of FIG. 1), the magnet 25is elevated and, through the magnetic attraction between the magnet 25and the armatures 19a, sustains the shield in the active, elevated,position as shown. As the arm 23 is drawn downwardly, the shield islikewise car- In this position the shield is eifecried down by thereason of the magnetic attraction between the magnet and the armatures19a, thus bringing the shield to the lowered or inspecting position.When the arm 23 is subsequently raised the magnetic attraction causesthe shield to lift with it, restoring the parts to the solid linepositions of FIG. 1.

It will be noted that the armatures 1% are located at substantiallyuniform peripheral spacings and are relatively close together. Thisassures that effective magnet attraction exists between the magnet 25and the armatures 19a, irrespective of the position of rotation of theshield within the envelope 1. It is thus unnecessary to confine theshield insofar as its position of rotation is concerned, and it may, asshown, be free to rotate within the envelope.

FIGS. 5 and 6 show an alternative form of the structure of the presentinvention. In this construction the envelope 1 defines a vacuum space 2within which the electrode rods 6 and 7 and electrodes 8 and 9 aredisposed as described above in relation to PEG. 1. A pair of cylindricalshield members 28 and 29 are disposed within the vacuum space 2, asshown in FIGS. 5 and 6. Each of these shields is of stainless steel orsimilar material and encircles the axis of the switch as shown. Theupper edge or lip 39 of the lower shield 29 forms an annular edge asshown. The lower edge or lip 31 of the upper shield 28 telescopes withinlip 3% as shown to provide an uninterrupted shielding surface about theelectrodes when shields 28 and 235 are in the positions having noend-to-end spacing as shown by the soiid lines of FTG. 5.

Each shield 28 and 29 has a plurality of magnetic bars or armatures 32disposed about its periphery as shown. These coact with the respectivemagnets 34 to provide magnetic attraction holding the shields in axialregistration with the respective magnets. Each magnet 3-4 is mounted ona carrier 35 having a threaded bore which receives the screw 36, whichin turn is mounted on bearings 37 and is turnable through the rotationof the knob 33. Each magnet 34 is held by means (not shown) to preventit from rotating with the frictional forces of rotating shaft 36.

Shields 28 and 29 are moved to the retracted position definingend-to-end spacing by rotation of the knob 38. This causes the carriers35 to move the magnets 34 away from each other by reason of therespective right and left hand pitch of the screw mechanism. With theshields 8 and 2% in the retracted or end-to-cnd spaced positions, theaxial space between the lower edge 31 of the upper shield 28 and theupper edge 35 of the lower shield 29 permits the user to view theelectrodes and thereby ascertain their condition.

It will be appreciated that, although in the embodiments of FIGS. 1 and5, specific switch-associated magnetic means for moving the shield havebeen shown, such means are not essential to the switch itself and othermagnetic means, not associated with the switch, may be utilized.Similarly, in tl ese embodiments, many frictionreducing means, otherwheels or bearings may be used to facilitate movement of the shieldwithin the switch. Thus, for example, spring biased fingers may bearagainst the switch inner walls. Means (not shown) are provided forpreventing the control magnets from rotating as the control shaft isrotated.

FIG. 7 shows another form of the present invention. In this constructionthe envelope 1 defines a vacuum space 2; within the electrode rods 6 and7 and electrodes 8 and 9 are disposed as described above in relation tothe embodiment of HG. 1. In the embodiment of FIG. 7, a two-part movableopaque shield 39 is disposed between the inside face of the envelope 1and the electrodes 6 and '7. The shield is of stainless steel or asimilar material.

One part of the shield 39, indicated at th, is in the form of a cylinderimmovably disposed within the en velope 1 between the electrodes 8 and iand the envelope of the vaporized electrode material.

1 to protect portions of the envelope from condensation An opening orwindow 41 is provided in the wall of the fixed part 40 of the shield 3in registration with electrodes 8 and 9. The electrodes may be viewedthrough this window.

The other part of the shield 39 is a cover portion 42 adaptable to coverthe opening 41 in the fixed portion 40 of shield 39. The cover portion42 of the shield 39 is movable between an active position inregistration with the opening 41 in the fixed shield 46 (as shown insolid lines in FIG. 7) and a viewing position out of registration withthe opening (as shown in dotted lines in FIG. 7). This motion is made byactuating lifting button 45. The arm 46 and the crank arm 43 areinterconnected by lever 47. Lever 47 is pivotally connected to crank arm4-3, which pivots about fixed pivot 44. At its opposite end the lever 47is similarly pivoted to the arm 46, as shown. At intermediate point 47alever 47 is supported by a slidable pivot, thus causing lever 47 torotate clockwise and crank 43 to rotate counterclockwise as the arm 4sis lifted. The lengths of the respective lever arms provideamplification of movement between the lifting movement of arm 4-6 andthe resultant swinging movement of the crank 43, thus bringing theshield 42 out of registration with window 41 (as shown in the dottedlines) when the button is moved a relatively small distance. Theoperator can then view electrodes 8 and 9 and evaluate the condition ofthe same. When the electrodes have been inspected, the push button 45 ismoved downwardly by its weight and by spring Eda to restore part 42 toshielding position.

Arm 4(- extends through opening 48 in the glass envelope 1. A sleeve 4?,preferably of fernico, is embedded in envelope 1 at this opening andreceives bellows 59 to define a vacuum-tight seal over opening .8 andextending about the end of arm 46. Button 45 engages the closed end ofthe bellows 59 to push the same upwardly to raise arm 45 as desired.

Another modification of the present invention is shown in FIG. 8. Inthis form of the invention a two-part movable opaque shield, showngenerally at 52, is located between the inside face of the envelope 1and the electrodes 8 and 9 in much the same fashion as shown anddescribed with respect to the embodiment of FIG. 7. In the constructionof FIG. 8, the two-part shield is composed of a fixed part 51, immovablymounted by suitable support elements (not shown) and a movable portion52. An opening or window 54 is provided in the fixed part 51 of theshield unit 52 to permit viewing of the electrodes.

The movable portion of the shield 52 is comprised of a cover 53. Thiscover is adapted to register with and cover the opening 54 in the fixedpart 51 of the shield. It is attached to a crank arm which is rotated tomove cover 53 between an active position in registration with theopening 54 and a viewing position wherein said movable pontion is out ofregistration with the opening. The .arm 55 is rotatably supported bybearing 56, which is mounted in the wall of the envelope 1 as shown.

The arm 55 has an external bent operating portion 57. The arm 55terminates in a knob 58, which is rotatably supported thereon bybearings 59, as is more clearly shown in FIG. 9.

A vacuum-tight seal is provided about the opening in the envelope 1 inwhich the bearing 56 is mounted. This seal is defined by sleeve 50,preferabiy of fernico, which is embedded in envelope 1, as shown. Oneend of a bellows 51 is attached to this sleeve in a vacuum-tight seal.The opposite end of the bellows 61 is afiixed in vacuumtight seal to theknob 58, thereby completing the vacuum seal around the opening for thebearing 56 in the envelope 1.

The movable shield part 53 is moved between the active and inspectingpositions by rotation of the knob 53 about the orbit defined by theoffset of arm 55. It should be observed that the bellows 61 and knob 58do in FIG. 12.

' openings 66 in the fixed shield part 63.

Rather, the arm 55 rotates. within the knob 58 reason ofthe bearingsFIGS -13 are illustrative of still another embodiment of the presentinvention.

The fragmentary View of FIG. 10 shows a cylindrical envelope It whichdefines a vacuum space 2 within which a pair of electrodes 8 and d areaxially disposed as described above in relation to FIG. .1. The shields2 has a fixed cylindrical portion 63 with windows as and internalshutters or covers 65 adapted to cover the windows $6. in the releasedposition of FIG. 10, these covers register with openings 66 to completethe shield. In the raised position of FIG. 12, they are out ofregistration with the windows 66 and permit inspection of theelectrodes.

The fixed portion of the shield 63 is disposed coaxially vith theelectrodes 8 and 9 and substantially encloses the arcing surfacesthereof as shown in FIG. 10. Conducting material vaporized on motion ofsaid electrodes from circuitanaking to circuit-breaking relation thustends to condense upon the shield rather than on the inside face of theenvelope 1.

The movable portion of the shield 64 is comprised of covers otshutters65. As shown, these are disposed in close proximity to the inside faceof the fixed shield porttlOI'l es of the shield 62 and are adapted toregister with and completely cover the openings 66 in the fixed portionof the shield. A crank arm 67 is afiixed to each shutter portion 65 andis pivotally supported from the inside face of the fixed shield part 63by the respectivepin 67a, FIG. 13. Each shutter 65 is thus movablebetween the active shielding position of FIG. 10 and the lifted viewingposition of FIG. 12.

The upper movable electrode 6, FIG. 10, is provided with an annularcollar member 68 positioned slightly above the head portion 8 of saidelectrode. The collar I 68 extends radiallyoutward a distance sufiicientto engage the crank arms 67 when the electrode is lifted as shown insuch event, the collar 68 engages and thereby rotates each of the crankarms 67, and hence shutter .65. The shutters are then lifted out ofregistration with the openings 65 in the fixed shield 63, therebypermitting viewing of the electrodes 3 and 9 for inspection.

Upon reposition of the electrode 6 to the position of FIG. 10, thecollaras releases crank arms 67 and the movable shutters 65 drop back toregistration withthe The parts are ti us positioned in their active,shielding positions.

FiG. 11 is a cross-section view through axis 11-11 of FIG. 10, showingthe overhanging relationship between the crank arms 67 and the collar68. i

In the. apparatus of FIGS. 10-,13, the movable'eleo trode rod .6 hasthree operating positions. The first position (notshown) is the fullylowered position, where electrode 8. is in contact-making relation withelectrode 9. This is the normal circuit-conducting position. In thisposition, the collar 68 is out .or contact with the crank arms 67and'the shutters are in the vertical, window covering position showninFIG. 10. The second position 0 of the movable electrode rod 6 is thatshown in FIG. 10. This is the circuit-opening position. When the switchis carrying current, movement of the electrode rod 6 from thecircuit-making to the circuit-breaking position of FIG. 10 normallygives rise to an are between the electrodes that persist until naturalcurrent zero. It is this arc that its Circuit-breaking position of PEG.10. This further movement can only take place when the circuit isinterrupted, and hence cannot occur when there is metal vapor producedin the envelope 1. As shown in FIG. 12, the further movement of thatfigure is sutficient to raise the shields to clear the windows 66 andpermit visual inspection of the electrodes 3 and 9.

L1 FIGS. 14 and 15 a fixed gap vacuum device is shown in verticalsection. The device of FIG. 14 includes an evacuable envelope 7%containing electrodes 71 and '72 defining a gap 73. The enclosure isevacuated to a pressure of l()' mm. Hg or less and preferably less thanl0 mm. Hg. This devicemay be used as a spark gap, a lightning arresteror as a triggered vacuum gap. A protective shield '74 rests uponinsulating member 75 within envelope 7'9 and is slidably movable alongthe longitudinal axis of the de ice. Motion between the protectingposition, shown in FIG. 14, and the viewing position, shown in FIG. 15,may be eiiectuated by inverting the device so that shield '74 slides bygravity and exposes the electrodes for viewing.

While I have shown and described specific embodiments of the presentinvention, it will of course be understood that various modificationsand alternative constructions may be made without departing from thepresent invention. I therefore intend by the appended claims to coverall such modifications and alternative constructions falling withintheir true spirit and scope.

What I claim as new and desired to secure by Letter Patent of the UnitedStates is:

1. .A vacuum switch comprising in combination: an envelope defining avacuum space and composed at least in partof a transparent body throughwhich the interior of the space may be viewed; a pair of electrodeswithin the vacuum space, and movable between a spaced circuitb-ealn'ngrelation and a containing circuit-making relation, saidelectrodes beingactive on motion from the circuibmalring to circuit-breaking relation togenerate vaporized conducting material that tends to condense in aconducting coating on the inside face of said part of the envelope, saidelectrodes being positioned within the en velope-in locations viewablefrom outside the envelope and through said part of the envelope; movableopaque shield means located between the inside face of the envelope andthe electrodes, said shield means being movable independent of thecircuit-making and circuit-breaking movements of said electrodes betweenan active position in registration with and protecting said part of theenvelope and a viewing position out of re istration with said part ofthe envelope to permit viewing of the electrodes; and means outside theenvelope operable to move the shield means at will between the activeand viewing positions. I

2. A vacuum switch comprising in combination: a cylindrical envelopehaving an axis, defining a vacuum space having an interior cylindricalface, and composed at least in part of a transparent body through whichthe interior of the space may be viewed; a pair of electrodes within thevacuum space, and movable in relation to each other and in the directionof said axis between an axially spaced circuit-breaking relation and anaxially contacting circuit-making relation, said electrodes being activeon motion from the circuit-making to the circuitvbreaking relation togenerate vaporized conducting material that tends to condense 'in aconducting coating on the inside face of said part of the envelope, saidelectrode being positioned within the envelope in locations viewablefrom outside the envelope and through said part of the envelope; anaxially movable opaque means telescopically received in said envelope,in juxtaposition with said face, and adapted to move axially therein,said shield means being movable between an active position inregistration with and protecting said part of the envelope and a viewingposition out of registration with said part of the envelope to permitviewing of the electrodes; and means operable from outside the envelopeto move the shield means at will relative to said electrodes between theactive and viewing positions.

3. A vacuum switch comprising in combination: an envelope having a wallportion defining a vacuum space having an inside face and composed atleast tin part of a transparent body through which the interior of thespace may be viewed; a pair of electrodes within the vacuum space andmovable between a spaced circuit-breaking relation and a contactingcircuit-making relation, said electrodes being active on motion from thecircuit-making to =circuit-breal ing relation to generate vaporizedconducting material that tends to condense in a conducting coating onthe inside face of said part of the envelope, said electrodes beingpositioned within the envelope in locations viewable from outside theenvelope and through said part of the envelope; movable opaque shieldmeans located between the inside face of the envelope and theelectrodes, said shield means being movable between an active positionin registration with and protecting said part of the envelope and aviewing position out of registration with said part of the envelope topermit viewing of the electrodes, at least a part of the shield meansduring such movement being constructed and arranged to move in a pathgenerally parallel and adjacent to the inside face of the envelope, theshield means further defining magnetic armature elements at said part;and magnet means disposed outside the envelope and adapted to registerwith the armature to move the shield means rela tive to said electrodesbetween the active and viewing positions.

4. A vacuum switch comprising in combination: a cylindrical envelopehaving an axis, defining a vacuum space having an interior cylindricalface, and composed at least in part of a transparent body through whichthe interior of the space may be viewed; a pair of electrodes within thevacuum space, and movable along said axis in relation to each otherbetween an axially spaced circuit-breaking relation and an axiallycontacting circuitmaking relation, said electrodes being active onmotion from the circuit-making to the circuit-breaking relation togenerate vaporized conducting material that tends to condense in aconducting coating on the inside face of said part of the envelope, saidelectrodes being positioned within the envelope in locations viewablefrom outside the envelope and through said part of the envelope; a pairof axially movable opaque shields telescopically received in saidenvelope and adapted to move axially therein, said shield means beingmovable relative to said electrodes between an active position inend-to-end relation and protecting said part of the envelope and aviewing position with end-to-end spacing to permit viewing of theelectrodes; and means operable from outside the envelope to move thepair of shields at will between the active and viewing positions.

5. A vacuum switch comprising in combination: an envelope defining avacuum space and composed at least in part of a transparent body throughwhich the interior of the space may be viewed; a pair of electrodeswithin the vacuum space, and movable between a spaced circuit-breakingrelation and a contacting circuit-making relation, said electrodes beingactive on motion from the circuit-making to circuit-breaking relation togenerate vaporized conducting material that tends to condense in aconducting coating on the inside face of said part of the envelope, saidelectrodes being positioned within the envelope in locations viewablefrom outside the envelope and through said part of the envelope;two-part movable opaque shield means located between the inside face ofthe envelope and the electrodes, one part of said shield means being infixed position and disposed between the electrodes and the envelope toprotect portions of the envelope from condensation of vaporizedelectrode ma terial and defining a Window in registration with said partof the envelope and through which the electrodes may be viewed, theother part of said shield means being a cover for said window movablebetween an active position in registration therewith and protecting saidpart of the envelope and a viewing position out of registration withsaid window to permit viewing of the electrodes; and means operable fromoutside the envelope to move the shield means at will relative to saidelectrodes between the active and viewing positions.

6. A vacuum switch comprising in combination: an envelope defining avacuum space having an inside face, and composed at least in part of atransparent body through which the interior of the space may be viewed;a pair of electrodes within the vacuum space, and movable between aspaced circuit-breaking relation and a contacting circuit-makingrelation, said electrodes being active on motion from the circuit-makingto circuit-breaking relation to generate vaporized conducting materialthat tends to condense in a conducting coating on the inside face ofsaid part of the envelope, said electrodes being positioned within theenvelope in locations viewable from outside the envelope and throughsaid part of the envelope, at least one of said electrodes beingadditionally movable beyond the circuit-breaking relation; means to movethe electrodes between circuit-making and circuit-breaking relation tomake and break the circuit and, at will, to move said one electrodebeyond circuit-breaking relation, movable opaque shield means locatedbetween the inside face of the envelope and the electrodes, said shieldmeans being movable between an active position in registration with andprotecting said part of the envelope and a viewing position out ofregistration with said part of the envelope to permit viewing of saidelectrodes; said one electrode and said shield means havinginterchanging conformations effective to engage and move the shield toviewing position when said electrode is moved beyond circuit-breakingposition.

7. A vacuum switch comprising in combination; an envelope defining avacuum space and composed at least in part of a transparent body throughwhich the interior of the space may be viewed; a pair of electrodeswithin the vacuum space, and movable between a spaced circuit-breakingrelation and a contacting circuit-making relation, said pair ofelectrodes being active on motion from the circuit-making tocircuit-breaking relation to generate vaporized conducting material thattends to condense in a conducting coating on the inside face of saidpart of the envelope, said electrodes being positioned within theenvelope in locations viewable from outside the envelope and throughsaid part of the envelope; a movable opaque shield located between theinside face of the envelope and the electrodes, said shield means beingmovable relative to said electrodes between an active position inregistration with and protecting said part of the envelope and a viewingposition out of registration with said parts of the envelope to permitviewing of the electrodes in response to means external of saidenvelope.

8. A vacuum gap device comprising in combination: an envelope defining avacuum space and composed at least in part of a transparent body throughwhich the interior of said space may be viewed; a pair of electrodeswithin the vacuum space adapted to form therebetween a vacuum gap forsustaining a high current electric are, said electrodes upon thesustaining of an electric are being the source of vaporized conductingmaterial that tends to condense in a conducting coating upon the insideface of said part of the envelope, said electrodes being positionedwithin the envelope in locations viewable from outside the envelope andthrough said part of the envelope; movable opaque shield means locatedbetween the inside face of the envelope and the electrodes, said shieldmeans being movable relative to said envelope and said electrodesbetween an active position in registration with and protecting said partof the envelope and a viewing position out of registration with saidpart of the envelope to permit enemas a viewing of the electrodesresponse to means external of said envelope. a V

9. A vacuum gap device comprising in combination: a cylindrical envelopehaving an axis, defining a vacuum space having an interior cylindricalface, and composed at least in part of a transparent body through whichthe interior of the space may be viewed; a pair of electro es within thevacuum space adapted to define therebetween a vacuum gap for sustaininga high current electric arc in vacuo, said electrodes being the sourceduring arcing of vaporized conductingnmaterials that tends to condensein a conducting coating on the inside of said part of the envelope, saidelectrodes being positioned within the envelope at locations-viewablefrom outside the envelope and through said part of the envelope; anaxially movable opaque means telescopically receivable in said envelopein justaposition with said face and adapted to move axially relative tosaid envelope and said electrodes, said shield means being movablebetween an active position in registration with and protecting said partof the envelope and a viewing position out of registration with saidpart of the envelope to permit viewing of the electrodes, said motionbeing in response to means external of said envelope. a

' 10. A vacuum gap device comprising in combination: an envelopedefining a vacuum space and composed at least in part of a transparentbody through which the in-.

terior of said space may be viewed; a pair of fixed electrodes Withinthe vacuum space adapted upon the application of an overvolta ge tosustain a high current electric arc, said electrodes upon sustaining ofan electric are being the source of vaporized conducting, material thattends to condense in a conducting coating upon the inside face ofsaidnpart of the envelope, said electrodes being positioned within theenvelope in locations viewable from outside the envelope and throughsaid part of the envelope; movable opaque shield means located betweenthe inside face of the envelope and the electrodes, said shield means"being movable between an active position in registration with andprotecting said part of the envelope and a viewing position out ofregistration with said part of the envelope to permit a viewing of theelectrodes, said motion being in response to the force of gravity actingon said shield.

11. A vacuum gap device comprising in combination: a cylindricalenvelope having an axis, defining a vacuum space having an interiorcylindrical face, and composed at least in part of a transparent bodythrough which the interior of the space may be viewed; a pair of fixedelectrodes within the vacuum space adapted upon an application of anovervoltage to sustain a high current electric are, said electrodesbeing the source during arcing of vaporized conducting material thattends to condense in a conducting coating on the inside of said part ofthe envelope, said electrodes being positioned within the envelope inlocations viewable from outside the envelope and through said part ofthe envelope; and axially movable opaque means telescopically receivablein said envelope in juxtaposition with said face and adapted to moveaxially therewith, said shield means being movable between an activeposition in registration with and pro- Cal tecting said part of theenvelope and a viewing position out of registration with said part ofthe envelope to premit viewing of the electrodes, said motion being inresponse to an externally applied force.

'i zeferenees'Cited in the tile of this patent UNITED STATES PATENTS1,875,765 Scherbius Sept. 6, 1932

1. A VACUUM SWITCH COMPRISING IN COMBINATION: AN ENVELOPE DEFINING AVACUUM SPACE AND COMPOSED AT LEAST IN PART OF TRANSPARENT BODY THROUGHWHICH THE INTERIOR OF THE SPACE MAY BE VIEWED; A PAIR OF ELECTRODESWITHIN THE VACUUM SPACE, AND MOVABLE BETWEEN A SPACED CIRCUITBREAKINGRELATION AND A CONTAINING CIRCUIT-MAKING RELATION, SAID ELECTRODES BEINGACTIVE ON MOTION FROM THE CIRCUIT-MAKING TO CIRCUIT-BREAKING RELATION TOGENERATE VAPORIZED CONDUCTING MATERIAL THAT TENDS TO CONDENSE IN ACONDUCTING COATING ON THE INSIDE FACE OF SAID PART OF THE ENVELOPE, SAIDELECTRODES BEING POSITIONED WITHIN THE ENVELOPE IN LOCATIONS VIEWABLEFROM OUTSIDE THE ENVELOPE AND THROUGH SAID PART OF THE ENVELOPE; MOVABLEOPAQUE SHIELD MEANS LOCATED BETWEEN THE INSIDE FACE OF THE ENVELOPE ANDTHE ELECTRODES, SAID SHIELD MEANS BEING MOVABLE INDEPENDENT OF THECIRCUIT-MAKING END CIRCUIT-BREAKING MOVEMENTS OF SAID ELECTRODES BETWEENAN ACTIVE POSITION IN REGISTERATION WITH AND PROTECTING SAID PART OF THEENVELOPE AND A VIEWING POSITION OUT OF REGISTRATION WITH SAID